--We continued our studies of the CA2 region of the hippocampus where the Oxtr and Avpr1b are located. The CA2 area is an important, although relatively unexplored, component of the hippocampus. We are studying the role of various receptors and in the CA2 by crossing floxed receptor lines with Oxtr and Avpr1b-cre expressing lines. We are studying the resultant behaviors, especially as they relate to aggression and learning and memory. --We published our first study using optogenetics of the CA2's role in social behavior and memory. We showed that stimulation of vasopressinergic innervation of CA2 from the paraventricular nucleus enhanced social memory. We are continuing to use optogenetics to study the role of the CA2 in behavior. We are examining the input to CA2 from other regions as well. We are examining the effects of this stimulation on aged mice.